An optical body that an optical functional layer interleaved between the first layer and the second layer is disclosed in the patent document 1. The optical functional layer is formed of electro-optical material including PLZT or other material which can control refractive index with applied voltage. Each of the first layer and the second layer is a reflective layer, so that the body composed of the first layer and the second layer constitutes a resonator. Light incident from the first layer is multiply-reflected between the first layer and the second layer. Then, the light is outputted from the first layer. Resonant wavelength of the resonator is controlled by changing refractive index of the optical functional layer. Accordingly, by controlling electric field applied to the optical functional layer, the refractive index of the optical functional layer is changed to make reflected quantity of incident light from the first layer controllable, namely light intensity outputted from the first layer controllable (as referred to FIG. 4 of the patent document).